1. Field of the Invention
The present invention generally relates to electro-magnetic transducers, and more particularly to a speaker having a voice coil.
2. Description of Related Art
In recent years, with the proliferation of slim-type electronic devices such as liquid crystal display devices, mobile telephones, there is a demand for thin-type and slim-type speakers with high performance. Generally, a speaker includes a magnetic circuit system for generating electro-magnetic force to drive a coil thereof to vibrate. Typically, the magnetic circuit system includes a yoke, a magnet positioned on the yoke, and a top plate attached to the magnet. A magnetic gap is formed between the yoke and the magnet. If a coil is suspended in the magnetic gap, when electrified, the coil will be given a magnetizing force, and the force is determined by the product of magnetic flux B, displacement of the coil L, and current applied on the coil. Production of B and L is called magnetizing force factor.
A voice coil used in a related speaker comprises two parallel linear members, and two arc members connecting two ends of the linear members respectively. The linear members and the arc members define a closed loop, like a standard run track. The arc member is generally a half circle. A speaker with such a coil has low sensitivity because it increases the length of the voice coil but contributes little for sensitivity.
So, it is necessary to provide an improved voice coil and a speaker using the voice coil for solving the problems mentioned above.
Many aspects of the embodiments can be better understood with reference to the drawings mentioned above. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.